1 Kh Training April 2005. 2 Gudiance on the selection of Kh Soil Soil to Rock Rock Soil Soil to Rock Rock

1

Kh Training

April 2005

2

Gudiance on the selection of Kh

• Soil

• Soil to Rock

• Rock

• Soil

• Soil to Rock

• Rock

3

SOIL

• The following slides relate Relative density and Consistency of soils to the Material Strength in Chapter 52 – Tables 52-2 and 52-3.

• The following slides relate Relative density and Consistency of soils to the Material Strength in Chapter 52 – Tables 52-2 and 52-3.

4

Soil

• Massive Jointed Cohesive

• Cohesive

• Low Plastic Cohesionless

• Non-Plastic Cohesionless

• Massive Jointed Cohesive

• Cohesive

• Low Plastic Cohesionless

• Non-Plastic Cohesionless

5

Cohesive

• Field Tests

• Lab Tests

• The PI of the Soils is greater than 10

• Field Tests

• Lab Tests

• The PI of the Soils is greater than 10

6

Lab. Data

• Natural moisture content %

• Specific Gravity Gs

• Liquid Limit LL

• Plasticity Index PI

• Clay Fraction (%<0.002mm)

• Unconfined Compression Strength (psf)

7

Characterizing Clays

Plasticity Index - The numerical difference between the Liquid Limit water content and the Plastic Limit water content

PI = LL - PL

8

Consistency of Clays

• To evaluate, clays must be saturated

• Saturation establishes base line for comparisons -even soft clays will become firm when dried

• Saturated consistency strong indicator of engineering behavior

• Water has zero shear strength

• To evaluate, clays must be saturated

• Saturation establishes base line for comparisons -even soft clays will become firm when dried

• Saturated consistency strong indicator of engineering behavior

• Water has zero shear strength

9

Steps in Evaluating Consistency of Saturated Clay

• Obtain data - LL, PI, either dry or wsat(%)

• Calculate PL (not usually reported) PL = LL - PI

Liquid LimitPlastic Limit

Establish location of wsat % on diagram

v/softsoftmediumstiff

10

Evaluating Consistency of Saturated Clay

• Steps to Evaluate– For saturated deposit, obtain sample and

measure oven dry w(%)– For unsaturated deposit, measure dry density,

assume value for Gs and calculate theoretical saturated w(%)

1001

(%)

sd

wsat Gw

11

1001

(%)

sd

wsat Gw

Example

What is the saturated water content of the following clay compared to its LL and PL?

Given: LL = 59, PI = 36, dry = 1.28 g/cm3Assume Gs = 2.70

12

Consistency and Atterberg Limits

Begin Constructing a consistency diagram by locating the LL value of 59

Liquid Limit 59

13


Next, calculate the Plastic Limit, which is equal to the LL minus the PI and plot that

PL = 59 - 36 = 23

Liquid LimitLiquid Limit 59 59

Plastic Limit 23

14


Now, divide the range between the LL and PL into thirds (PI 3) - (36 3 = 12)

Liquid Limit 59

Plastic Limit 23

v/soft

35 47

15


• Now label the ranges as shown

Liquid Limit 59

Plastic Limit 23

v/softsoftmediumstiffv/stiff

35 47

16


Next, Calculate the saturated water content, given that dry = 1.28 g/cm3 and Gs = 2.70

%41.11002.70

1

1.28

1.0(%)wsat

17


• Plot the saturated water content on the diagram to identify its consistency

Liquid Limit 59

Plastic Limit 23

wsat % = 41 %, medium consistency

v/softsoftmediumstiffv/stiff35 47

18

Liquidity Index

• Another method for quickly assessing the saturated consistency of a clay uses a term Liquidity Index

• Liquidity Index is defined from a simple equation that expresses numerically where the saturated water content is in relation to the Atterberg Limits

19

Liquidity Index Equation

PI

PILLw

PI

PLwLI satsat

If wsat = Liquid Limit, then LI = 1.0

If wsat = Plastic Limit, then LI = 0

20

Summary of Clay Problem Soils

• Problem Clays are very soft clays with liquidity index 1, or

• Stiff to very stiff clays with liquidity index 0

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Liquidity Index and Saturated Consistency

Liquidity Index < 0 0 to 0.330.33 to 0.670.67 to 1.00 > 1.00

Liquidity Index < 0 0 to 0.330.33 to 0.670.67 to 1.00 > 1.00

SaturatedConsistencyvery stiffstiffmediumsoftvery soft

SaturatedConsistencyvery stiffstiffmediumsoftvery soft

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What is the liquidity index of the Example Soil?

• Given that wsat = 41%, LL = 59, and PI = 36, entering these terms in the LI equation:

PI

PILLw

PI

PLwLI satsat

5036

365941.

PI

PLwLI sat

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Conclusion - Medium Consistency

Liquidity Index < 0< 0 0 to 0.330 to 0.330.33 to 0.670.67 to 1.000.67 to 1.00 > 1.00> 1.00

SaturatedConsistencyvery stiffvery stiffstiffstiffmediumsoftsoftvery softvery soft

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Field Estimate of Consistency

Consistency

– Very Soft

– SoftSoft

– MediumMedium

– StiffStiff

– V/Stiff to HardV/Stiff to Hard

Rule of Thumb

Thumb will penetrate soil more than 1-inch. Extrudes between fingers when squeezed in fist

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Consistency

Very SoftVery Soft

Soft

MediumMedium

StiffStiff

V/Stiff to HardV/Stiff to Hard

Rule of Thumb

Thumb will penetrate soil about 1-inch. Easily molded in fingers

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Consistency

Very SoftVery Soft

SoftSoft

Medium

StiffStiff


Rule of Thumb

Thumb will not penetrate soil, but will indent about 1/4 inch. Molded by finger pressure

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Consistency

Very SoftVery Soft

SoftSoft

MediumMedium

Stiff


Rule of Thumb

Thumb will not indent soil, but soil can be indented with thumbnail.

28


Consistency

Very SoftVery Soft

SoftSoft

MediumMedium

StiffStiff

V/Stiff to Hard

Rule of Thumb

Can only be marked with knife - not indented with thumbnail.

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Soft Clays - Field EstimatesSPT,

BLOWS/FOOT CONSISTENCY C VALUE, PSF

< 2 Very Soft – extrudedbetween fingers

< 250

2 – 4 Soft – Molded by lightfinger pressure

250-500

4 – 8 Medium – Molded bystrong finger pressure

500 – 1000

8 – 15 Stiff – Indented by thumbbut not penetrated

1000 – 2000

15 – 30 Very Stiff – Indented byThumbnail

2000 – 4000

> 30 Hard – Indented withKnife

> 4000

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Estimating Effective angle for claysKinney's Correlation

20

25

30

35

0 10 20 30 40 50 60 70 80 90

Plasticity Index (PI)

Effe

ctiv

e a

ngle

, de

gree

s

31

SOILS WITH PI LESS THAN 10SOILS WITH PI LESS THAN 10

• Methods to estimate RELATIVE DENSITY for nonplastic soils

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Relative Density

• Studies for the Alaska pipeline established empirical estimates of relative density for various soil types, based on the measured in place density of the soils

• Average values of minimum and maximum index density for the project were used

• May be useful for preliminary estimates

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80

90

100

110

120

130

140

0 10 20 30 40 50 60 70 80 90 100

Relative Density, %

Dry

Den

sity

, p

cf

sand and silty sand

Gravelly sand

Reference - Donovan, N.C. and Sukhmander Singh, "Liquefaction Criteria for the Trans-Alaska Pipeline." Liquefaction Problems in Geotechnical Engineering, ASCE Specialty Session, Philadelphia, PA, 1976.

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Relative Density

• Because saturated water content is related to dry density, a chart can be derived relating in place saturated water content to relative density, as shown on the following slide

1001

(%)

sd

wsat Gw

35

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70 80 90 100

Relative Density, %

Sat

ura

ted

Wat

er C

on

ten

t, %

Reference Donovan, N.C. and Sukhmander Singh, "Liquefaction Criteria for ભthe Trans-Alaska Pipeline." Liquefaction Problems in Geotechnical Engineering, ASCE Specialty Session, Philadelphia, PA, 1976.

Average

Chart is for silty sands (SM)

Other information on Relative Density

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Field Estimates for Relative Density

• Relative Density

– Very Loose

– LooseLoose

– MediumMedium

– DenseDense

– Very DenseVery Dense

Description

1/2” Reinforcing rod

can be pushed easily

by hand into soil

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– Very LooseVery Loose

– Loose

– MediumMedium

– DenseDense


Description

Can be excavated

with a spade. A

wooden peg 2”x

2”can easily be drive

to depth of

6 ”.

38




– LooseLoose

– Medium

– DenseDense


Description

Easily penetrated

with a 1/2”

reinforcing rod

driven with a 5

pound hammer

39




– LooseLoose

– MediumMedium

– Dense


Description

Requires a pick for

excavation. Wooden

peg 2”x 2”is hard to

drive beyond 6 ”.

40




– LooseLoose

– MediumMedium

– DenseDense

– Very Dense

Description

Penetrated only a

few centimeters with

a 1/2” reinforcing

rod driven with a 5

pound hammer

41

Fort Worth Relative Density Study

• NRCS lab in Fort Worth studied 28 filter sands and used some published data

• Minimum and Maximum Index Densities were performed on each sample

• A 1 point dry Standard Proctor energy mold was also prepared for each sample.

• Values of 50% and 70% relative density were plotted against the 1 point Proctor value

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70 % Relative Density vs. 1 Point Proctor

90

95

100

105

110

115

120

125

130

90 100 110 120 130

Field 1 Point Proctor Test Dry Density, pcf

70 %

Rel

ativ

e D

ensi

ty

70 %RD = 1 Point line

Best fit correlation

43

• Conclusion is that 100 % of the Field

1 point Proctor dry test is about

equal to 70 % relative density

70 % Relative Density Vs. 1 Point Proctor

44


90

95

100

105

110

115

120

125

90 95 100 105 110 115 120 125 130

Field 1 pointdry density

50 %

Rd

95 % of 1 point

best fit line

45

• Conclusion is that 95 % of the field 1

point Proctor dry test is about

equal to 50 % relative density


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D70 = 1.075 x d 1pt -9.61,

for RD70 and d 1pt in lb/ft3

D50 = 1.07 x d 1pt - 12.5,

for RD50 and d 1pt in lb/ft3

Relative Density Estimates from FW SML Study

47

• Example Relative Density Estimates

–Given: 1 Point Proctor Testd = 105.5 pcf

–Estimate 70 % and 50% Relative Density from the Fort Worth equations

–Given that measured d is 98.7, evaluate state of compaction of sand.

Relative Density Estimates from FW SML Study

48

D70 = 1.075 x d 1pt -9.61, = 1.075 x 105.5 -9.61 = 103.8 pcf

D50 = 1.07 x d 1pt - 12.5, = 1.07 x 105.5 - 12.5

= 100.4

Solution to Example Problem

49


• Conclusion is that measured dry

density of 98.7 pcf is less than the

estimated 50% Relative Density dry

density value of 100.4 pcf

50


• Measured Dry Density is 98.7 pcf and Field 1 Point Dry Density is 105.5 pcf. Measured Dry Density then is 98.7 105.5 = 93.6 percent of the 1 Point Proctor -

• Again, by rule of thumb < 50% RD

51

Empirical Estimates for Sands and Gravels

• Empirical Estimates of Shear Strength Estimating effective friction angle

52

NRCS Correlations

25

30

35

40

45

50

15 25 35 45 55 65 75 85

Relative Density (%)

Eff

ecti

ve

an

gle

, deg

rees

Well-graded Sands and Gravels

Poorly Graded Sands

Silty Sands

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The End

Documents

1 Kh Training April 2005. 2 Gudiance on the selection of Kh Soil Soil to Rock Rock Soil Soil to Rock Rock